Fuel vaporization tends to decrease as ambient temperature decreases. This can make engine starting more difficult at lower temperatures because reduced fuel vaporization can result in an air-fuel mixture near the engine's spark plug that is less than the fuel's lower flammability limit. Further, lower rates of fuel vaporization may make engine starting particularly difficult for certain types of fuels (e.g., ethanol). One example way to improve fuel vaporization is described in U.S. Patent Application 2005/0263136. This patent application describes placing a heating coil around the nozzle of a port fuel injector. The heating coil is supplied electrical energy through an electrical connector that attaches to an engine wiring harness. Heat produced by the heating coil is conducted through the injector to heat fuel that resides within the injector. This heating apparatus purportedly improves fuel vaporization.
The above-mentioned system can also have several disadvantages. Namely, the system heats the injector through conducting heat from a source outside the injector body. Since the heat source is external to the injector, some energy intended to heat the injector is lost to heating the engine and may therefore be less efficient than is desired. In addition, the heating device requires an additional electrical connector to route power to the heating device. An additional connector increases the number of wires and connections. Therefore, system reliability may be reduced when such a system is used to increase the temperature of fuel injected to an engine. In addition, the system may be difficult to implement on direct injection engine because there may be less space available to place a heating coil around the injector nozzle.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method that offers substantial improvements.